title: Mineralogical controls on aluminum and magnesium in uranium mill tailings: Key Lake, Saskatchewan, Canada.
abstract: The mineralogy and evolution of Al and Mg in U mill tailings are poorly understood. Elemental analyses (ICP-MS) of both solid and aqueous phases show that precipitation of large masses of secondary Al and Mg mineral phases occurs throughout the raffinate neutralization process (pH 1-11) at the Key Lake U mill, Saskatchewan, Canada. Data from a suite of analytical methods (ICP-MS, EMPA, laboratory- and synchrotron-based XRD, ATR-IR, Raman, TEM, EDX, ED) and equilibrium thermodynamic modeling showed that nanoparticle-sized, spongy, porous, Mg-Al hydrotalcite is the dominant mineralogical control on Al and Mg in the neutralized raffinate (pH ≥ 6.7). The presence of this secondary Mg-Al hydrotalcite in mineral samples of both fresh and 15-year-old tailings indicates that the Mg-Al hydrotalcite is geochemically stable, even after >16 years in the oxic tailings body. Data shows an association between the Mg-Al hydrotalcite and both As and Ni and point to this Mg-Al hydrotalcite exerting a mineralogical control on the solubility of these contaminants.
authors.affiliation: Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada. mag346@mail.usask.ca
authors.forename: M A
authors.initials: MA
authors.lastname: Gomez
authors.forename: M J
authors.initials: MJ
authors.lastname: Hendry
authors.forename: J
authors.initials: J
authors.lastname: Koshinsky
authors.forename: J
authors.initials: J
authors.lastname: Essilfie-Dughan
authors.forename: S
authors.initials: S
authors.lastname: Paikaray
authors.forename: J
authors.initials: J
authors.lastname: Chen
mesh_terms: D000535:Aluminum / Q000032:analysis*; D008274:Magnesium / Q000032:analysis*; D046529:Microscopy, Electron, Transmission; D012525:Saskatchewan; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics; D014501:Uranium / Q000737:chemistry*
chemical_list: D014501:Uranium; D000535:Aluminum; D008274:Magnesium